Substrate having corrugated sheet(s) and channel(s) for treating exhaust gases of combustion engines

ABSTRACT

The present invention relates a substrate having corrugated sheet(s) and channel(s) for treating exhaust gases of combustion engines. The present invention also relates to methods for manufacturing and using said substrate having said open channel(s). The substrate ( 1 ) comprises at least one corrugated sheet ( 3 ) having depressions ( 3   d ) and one flat wire mesh sheet ( 2 ) having depressions ( 2   d ) which is connected to said corrugated sheet ( 3 ) and between said flat wire mesh sheet ( 2 ) and said corrugated sheet ( 3 ) there are at least partially open channels (POC) for exhaust gas (EG) flow, and the depth of depression ( 2   d ) of said flat wire mesh sheet ( 2 ) is 0.05-0.5 mm smaller than the height of the corrugation ( 3   c ) of said corrugated sheet ( 3 ).

The present invention relates a substrate having corrugated sheet(s) andchannel(s) for treating exhaust gases of combustion engines. The presentinvention also relates to methods for manufacturing said substratehaving said open channel(s).

BACKGROUND OF THE INVENTION

For the treatment of exhaust gases of combustion engines substrateshaving open or closed channels or combinations of those is used. In openchannels the exhaust gas is directly flowing through the substrate. Insubstrate having closed channels exhaust gas is forced to flow throughwalls, e.g. through ceramic or metallic porous walls. In open channelsthe reduction of gaseous impurities is often high but the reduction ofimpurity particles is low, e.g. from 10 to 15%. In closed channels/wallflow filters the reduction of gaseous impurities is high and also thereduction of impurity particles is high, e.g. from 70 to 99%. Theproblem in closed channels is the clogging of walls. Closedchannels/wall flow filters will gradually wholly clog if they are notcleaned. Pressure loss will also increase. One way to keep the channelsopen is to clean them continuously or periodically.

DISCLOSURE OF THE INVENTION

A substrate that efficiently reduces particles and gas impurities ofexhaust gas in open channels has now been invented. Accordingly a methodfor manufacturing said substrate has also been invented.

For this purpose, the invention is characterized in facts presented inthe independent claims. Some preferable embodiments of the invention aredisclosed in other claims.

Constructional embodiments of the invention are not limited in any way.According to an embodiment of the invention, the catalyst of theinvention can be present in several structures assembled parallel or inseries with respect to the flow direction or cascade withPOC/DPF-structure/substrates.

According to an embodiment of the invention the substrate comprisescorrugated sheet(s) having depressions connected to flat wire meshsheet(s) and between said flat wire mesh sheet and said corrugated sheetthere are at least partially channel(s) for exhaust gas flow and thedepth of depression is 0.05-0.5 mm smaller than the height of thecorrugation.

It has been surprisingly discovered that the reduction of particlesflowing in open channels is essentially improved. Also the reduction ofimpurity gases in at least partially open channels is improved.

Preferably the depth of the depression is 0.5-1.5 mm and the height ofthe corrugation is 1.0-3.0 mm. This combination is very effective bothin reduction of particles and in the reduction of impurity gases. Thedepressions can be e.g. 10-40 mm, such as 20-30 mm, from each other.

Exhaust gas can freely flow through partially open channels but on thesurfaces of sheet the gas flow rate is reduced due to irregular surfaceof wire mesh sheet(s) and due to depressions of sheets. These irregularsurfaces and depressions also mix the gas thus minimizing standarddeviation of gas retention time. The surfaces of wire mesh sheet(s) alsoact as an effect open particle trap for exhaust gas particles. Thiscombination adds contacts of impurity of gases and particles thus addingretention time and reduction of impurities and particles. Impurityparticles are more often attached to mesh sheet compared to smoothsheet. Especially heavy and large particles are attached on the surfacesof wire mesh sheet(s).

The reduction of particles is very much depending on the particle sourceand composition of particles. Particles can include various amountVolatile Organic Compounds (VOF's), solid carbon, sulphur, water andmetal oxides. A standard oxidation catalyst can oxidize majority VOF'sand reduce this way 10 to 60% of particle mass. With the new inventionit is possible to improve particle reduction even up to 80%. With thenew invention it is possible to improve reduction of gas impurities>90%.

An important character of new partially open channel is that it is notclogging at all or the clogging is minimal compared to closed channelsor filters, which will gradually wholly clog if they are not cleaned.This is very important and the substrate having at least partially openchannels according to the invention can be used in most demandingconditions and they are useful in many applications.

The particles attached to the surfaces of at least partially openchannel(s) break down to gaseous impurities, which further decompose toharmless compounds. Part of gas can flow through openings of meshsheet(s) and particles attach on surfaces of sheet(s). Also this leadsto better reduction of particles. On the other hand partially openchannels do not clog or the clogging is minimal and pressure loss andflow rate of gas are not reduced near the sheet(s). This reduces failurein operation thus adding efficiency of the partially open channel.

The shape of openings of mesh sheet(s) can vary. It can be canal-like,square-like, diamond-like or hole-like. E.g. in diamond-like mesh sheetthe wires can be at one level or they can be crosswise.

Pressure difference between sides of the mesh sheet(s) adds flowing ofexhaust gas through pores of the mesh sheet. This phenomenon leads toattachments of particles on support and better reduction of particlesfrom exhaust gas.

According to an embodiment of the invention said corrugated sheet is acorrugated wire mesh sheet. This adds contacts of impurity gases andparticles thus adding retention time and reduction of impurities. Thisleads to better reduction values of impurity particles of exhaust gas.Collision of gas also leads to better contact of gas with catalyticallyactive material thus improving reduction of gaseous impurities andadding retention time of particles in said substrate.

Preferably, there are open channels with both sizes of said mesh sheet.The structure of wire mesh sheet is simply, they are easy to manufactureand the reduction of particles is high compared e.g. smooth sheet usedin open channels.

According to an embodiment of the invention said flat wire mesh sheethas depressions. Also this adds reduction of impurity gases particles byreducing flow rate of impurity gases and adding attachment of particleson support.

According to an embodiment of the invention depressions of thecorrugated sheet have been matched to the depressions of the flat wiremesh sheet. This leads to better strength of the substrate because itslocking layers to each other.

According to an embodiment of the invention the median opening size ofmesh sheet is from 0.01 to 0.5 mm, preferably from 0.05 to 0.3 mm, suchas from 0.08 to 0.2 mm.

According to an embodiment of the invention the mesh diameter is0.08-0.24 mm. The mesh diameter is preferably 0.1-0.15 mm. Then themechanical strength is high and pressure loss of gas flow is low.

According to an embodiment of the invention mesh number of the meshsheet is from 30 to 300. At least part of exhaust gas can flow throughthe openings of mesh sheets. This leads to attachment of particles ofexhaust gas to the surfaces of support giving essentially betterreduction of particles.

According to an embodiment of the invention said flat wire mesh sheetand said corrugated sheet have been attached to each other bywelding/brazing. This leads to better strength of the substrate.

According to an embodiment of the invention said sheet(s) have been atleast partially covered by support and/or catalytic material. Preferablemedian pore size of said support is over 5 nm, preferably from 10 to 50nm, such as from 15 to 20 nm. Optimal pore size of the support alsodepends on exhaust gases and circumstances of gas flow near meshsheet(s). Exhaust gases can have e.g. median particle size from 5 to 200nm and median pore size can e.g. be from 5 to 20 nm.

Preferable support comprises coarse particles and/or fibres, which areprojecting out from the plane of said support. Preferably the supporthas the median particle size over 0.4 μm, such as from 1.5 to 3.5 μm.This essentially adds the adhesion of particles thus improving thereduction of particles in said substrate

According to an embodiment of the invention sheet(s) has (have) beenessentially covered with a support having the median particle size over1.4 μm and/or having pores over 10 nm. This also improves reduction ofimpurity particles by adding attachment of particles to sheets.

Particles of exhaust gas of combustion engines can be efficientlytreated with substrate having mesh sheet(s) partially open channelsaccording to the invention. The reduction of impurity particles issurprisingly high compared to traditional substrates. Also the reductionof gaseous impurities is high. The mesh sheet(s) according to theinvention does not clog or the clogging is minimal so that it does nothave effect s on flowing rate of exhaust gas in substrate. Also pressureloss in substrate is minimal.

The substrate can e.g. be a particle oxidation catalyst (POC) or SCRcatalyst. It can also be a hydrolysis catalyst. The substrate can bepreferably used to purify impurity particles of exhaust gases ofcombustion engines. The structure of substrate can vary. It can be e.g.wound or stacked or folded.

DETAILED DESCRIPTION OF THE INVENTION

Now some embodiments of the present invention will be described in moredetail with reference to the appended drawings.

FIG. 1 shows a substrate having corrugated sheet having depressions anda flat wire mesh sheet.

In FIG. 1 substrate 1 comprises corrugated smooth sheets 3 havingdepressions 3 d and flat wire mesh sheets 2 having depressions 2 d.These sheets are connected to each other and between said sheets 2, 3there are partially open channels POC for exhaust gas EG flow. Thedepressions 3 d of the corrugated sheet 3 has been matched to thedepressions 2 d of the flat wire mesh sheet 2. The depth of depression 2d of said flat wire mesh sheet 2 is smaller than the height of thecorrugation 3 c of said corrugated sheet 3. In this embodiment the depthof the depression 2 d, 3 d is about 1 mm and the height of thecorrugation 3 c is about 2 mm.

1. A substrate having corrugated sheet(s) and channel(s) for treatingexhaust gases of combustion engines, characterized in that the substrate(1) comprises at least one corrugated sheet (3) having depressions (3 d)and one flat wire mesh sheet (2) having depressions (2 d) which isconnected to said corrugated sheet (3) and between said flat wire meshsheet (2) and said corrugated sheet (3) there are at least partiallyopen channels (POC) for exhaust gas (EG) flow, and that the depth ofdepression (2 d) of said flat wire mesh sheet (2) is 0.05-0.5 mm smallerthan the height of the corrugation (3 c) of said corrugated sheet (3).2. A substrate according to claim 1, characterized in that saidcorrugated sheet (3) is a corrugated wire mesh sheet.
 3. A substrateaccording to claim 1, characterized in that said depressions (3 d) ofthe corrugated sheet (3) has been matched to the depressions (2 d) ofthe flat wire mesh sheet (2).
 4. A substrate according to claim 1,characterized in that the depth of the depression (2 d, 3 d) is 0.5-1.5mm.
 5. A substrate according to claim 1, characterized in that theheight of the corrugation (3 c) is 1.0-3.0 mm.
 6. A substrate accordingto claim 1, characterized in that mesh number of the mesh sheet is from30 to
 300. 7. A substrate according to claim 1, characterized in thatsaid flat wire mesh sheet (2) and said corrugated sheet (3) have beenattached to each other by welding or by brazing.
 8. A substrateaccording to claim 1, characterized in that said sheets (2, 3) have beenat least partially covered by support and/or catalytic material.
 9. Amethod for using a substrate according to claim 1 for purifying exhaustgases (EG).
 10. A method for manufacturing a substrate having corrugatedsheet(s) for treating exhaust gases of combustion engines, characterizedin that a flat wire mesh sheet (2) having depressions (2 d) is connectedto a corrugated sheet (3) having depressions (3 d) so that between saidflat wire mesh sheet (2) and said corrugated sheet (3) there are atleast partially open channels (POC) for exhaust gas (EG) flow, and thatthe depth of depression (3 d) being smaller than the height of thecorrugation (3 c).
 11. A method according to claim 9, characterized inthat said flat wire mesh sheet (2) is connected to said corrugated sheet(3) by rolling.
 12. A method according to claim 9, characterized in thatsaid flat wire mesh sheet (2) is connected to said corrugated sheet (3)by stacking or folding.
 13. A method according to claim 9, characterizedin that a flat wire mesh sheet (2) is connected to a corrugated sheet(3) by making depressions (2 d, 3 d) to said flat wire mesh sheet (2)and corrugated sheet (3) and matching these depressions (2 d, 3 d) toeach other.
 14. A method according to claim 9, characterized in thatsaid flat wire mesh sheet (2) and said corrugated sheet (3) are attachedto each other by welding or by brazing.
 15. A substrate according toclaim 2, characterized in that said depressions (3 d) of the corrugatedsheet (3) has been matched to the depressions (2 d) of the flat wiremesh sheet (2).
 16. A substrate according to claim 2, characterized inthat the depth of the depression (2 d, 3 d) is mm.
 17. A substrateaccording to claim 3, characterized in that the depth of the depression(2 d, 3 d) is mm.
 18. A substrate according to claim 2, characterized inthat the height of the corrugation (3 c) is mm.
 19. A substrateaccording to claim 3, characterized in that the height of thecorrugation (3 c) is mm.
 20. A substrate according to claim 4,characterized in that the height of the corrugation (3 c) is mm.